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B Is quantification random or pseudo-random?

  1. Mar 19, 2016 #1
    Is quantification, such as for instance with the build op of an interference pattern by individual photons, the measuring of quantum spin, or the measuring of polarized photons through a polarisation filter actually, really random, or is it possible that it might be pseudo-random?
  2. jcsd
  3. Mar 19, 2016 #2


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    There's no way of distinguishing a pseudo-random process whose internal mechanism is unknown from a random process, so yes, it is possible that the process is pseudo-random. We'd never know the difference though, which takes some of the fun out of the question.

    And do note that a local pseudo-random process would be an example of a local hidden variable theory (the hidden variables being the internal state of the random number generating process), and such theories are precluded by Bell's theorem. Thus, the random number generating process is necessarily non-local.
  4. Mar 19, 2016 #3
    I'm sure some or many people have considered it. So you are saying the two are indistiquishable. However, maybe for instance under Bohmian Mechanics, the mathematical framework is slightly different?

    I am also pondering this question. If very much or all particles in the universe are entangled, they should have some correlations in their properties, so that each particle effectively has no local purely random properties anymore?
    Last edited: Mar 19, 2016
  5. Mar 19, 2016 #4


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    It's always been that way. A quantum system is described by a single state vector even when we find it convenient to think of the system as containing multiple particles and to call some observables of the system properties of one particle and others properties of the other. Some preparations of such a system lead to states in which the correlation between these groups of observables is negligible or zero, and then we can calculate as if we're working with multiple isolated particles each with its own wave function. There's an analogy with classical mechanics here: we calculate the orbit of the planets around the sun as if the solar system is the only thing in the universe, even though it's surrounded by an entire galaxy.

    None of this has any bearing on whether the randomness inherent in the Born rule is "really random" or pseudo-random and driven by an underlying deterministic theory of which we are unaware.
  6. Mar 19, 2016 #5
    OK. Then I'm on the wrong track.

    (And consequently, QM is a great, incomprehensible mystery again :wink: )
    Last edited: Mar 19, 2016
  7. Mar 19, 2016 #6


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    Start with a proper textbook.
  8. Mar 28, 2016 #7
    I thought of another way to phrase my question:

    I learned that macro objects can also be regarded as a single wavefunction (is that correct?). If that was the case, we could be simultaneously alive and dead, as well as a whole lot of different things (is that correct?). Now, since we see in the macroworld that macro objects have a pretty consistent appearance, does that mean that the probabilities their wavefunction gives rise to need to be 'stabilized' in some manner, for instance, by correlating the probabilities of their wavefunction with all the various probabilities in their surroundings?

    Tell me if I'm being stupid again :wink:

    (BTW, reading 'Theoretical Minimum' now - it's awesome! :smile: )

    Update: this post introduces a thread on the unitarity of an open system (of rather the lack thereof). Maybe that is what I mean?
    Last edited: Mar 28, 2016
  9. Mar 28, 2016 #8
    I don't know the answer to your more recent question - but let me tackle your first one.
    A less ambiguous term than random is "stochastic". It means not only completely unpredictable, but occurring entirely by chance. If quantum events were purely stochastic, they would be independent of all other events in the universe - or at least there would be a component of the events that was entirely independent of anything else. So, just as local pseudo-random processes (as described by Nugatory) can be eliminated, purely stochastic processes (which are inherently local) can also be eliminated.

    To be certain, this does not mean that quantization cannot be "trusted to be random". They can be, for all practical purposes, random.
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